Two n-Unit Cold-Standby Systems with an Erlang Distribution

This paper presents two n-unit cold-standby systems. In model 1, the operating unit has general-Erlang failure time distribution. It fails in any one of the Erlang phases. the repair-time distribution of a failed unit is general. Model 2 presents the case when the operating unit has general failure-time distribution and the failed unit has general-Erlang repair-time distribution. The main paper describes the models and a Supplement presents the transition probability functions, availability and reliability equations. Renewal theory is used to formulate the equations.